1. Field of the Invention
The present invention relates to improvements in apparatuses for refining pulp and to a method for the refining of pulp.
2. Description of the Prior Art
Pulp refiners of the type comprising a pair of refiner members having opposed facing refining surfaces defining a gap therebetween for receiving a material to be refined are well known in the art.
For instance, U.S. Pat. No. 4,874,136 issued on Oct. 17, 1989 to Applicant discloses a pulp refiner comprising a pair of cooperating refiner members having identical plain spiral refining edges. The spiral refining edges face each other and have many intersections, characterized as crossovers. The discs are normally driven at equal rotary speeds but in opposite directions. As a result, a locus of any such crossover moves straight along a stationary line as a radius.
Although such cooperating spiral patterns have been found suitable in that they apply a smooth, low-audible, screw-like, sliding-pinching action to the material to be refined, thereby reducing wear of and power consumption, it has been found that when both plain spiral patterns pump outward, the flow is strong but the refining is weak, leaving a deficiency problem for some grades of pulp.
It is therefore an aim of the present invention to improve pulp refining using spiral refining patterns.
It is also an aim of the present invention to increase crossovers and hydraulic shear. in a refining zone.
Therefore, in accordance with the present invention, there is provided a pair of cooperating refiner members having opposed facing refining surfaces defining a gap therebetween for receiving a material to be refined, each said refining surface being formed with alternating grooves and lands, the lands of one refining surface intersecting the lands of the other refining surface to form crossovers therewith, wherein at least one of said refiner member is rotatable, and wherein said grooves and lands defined in said at least one refiner member extend in a continuous spiral pattern of at least one revolution for providing a screw-like pumping action on the material when said at least one refiner member is rotated, said continuous spiral pattern of said at least one refiner member being different from a refining pattern of the other cooperating refiner member to provide additional crossovers and increased hydraulic shear between said refining surfaces compared to refiner members having similar patterns of grooves and lands.
In accordance with a further general aspect of the present invention, there is provided a pair of cooperating refiner members, at least one of said refiner member being rotatable and having a sinuous spiral refining pattern defined thereon in order to increase an area of crossovers between said refiner members.
In accordance with a further general aspect of the present invention, there is provided a method of refining material, comprising the steps of: providing a pair of refining surfaces having different refining patterns, operating said refining surfaces by rotating at least one of said refining surfaces to impart a screw-like pumping and pinching action to the material to be refined, and introducing the material to be refined between said refining surfaces.